Powdered metal has a number of increasingly important applications. It has long been used for making porous metal parts and in the more recent past it has generated great interest in the manufacture of high strength parts of a compound shape. Such parts as are frequently found on aircrafts, spaceships, and the like where minimum weight and high strength are critical. They are made from specially alloyed metals which have the desired characteristics. The parts were heretofore cast and/or forged and then machined to the desired dimensions.
This wastes a great amount of expensive metal, and requires complicated and time-consuming metal-working operations. The costs of such parts is therefore high.
It has been recognized that high-strength parts, with or without compound shapes and surfaces can be made from powder of the alloy in question by pressing and then sintering the powder. Material wastes are thereby greatly reduced or eliminated and in many instances parts can be made to their finished dimensions to eliminate complicated machining. Substantial cost savings can thereby be achieved.
Difficulties are encountered, however, in making the required high volume of metal powder. The powder must be of the correct particle size and possess proper physical and chemical characteristics; contamination of the powder cannot be tolerated. Such contamination may result from chemical reactions between the heated or molten metal, and the surrounding atmosphere or from substances with which the molten metal comes into contact or when the metal is mechanically powderized, from an intermixing of abrasive agents, chips and the like with the powder.
There is, therefore, a present need for a method of transforming solid metal into powder without contaminating the resulting powder. Furthermore, to enable the economic exploitation of the above-mentioned metal powder forming and sintering processes, it is necessary that uncontaminated, high purity powder can be made at a low cost.